bug#41884: 27.0.91; `C-h f whitespace-mode' doesn't say that it's a minor mode

[Drew Adams <drew.adams@oracle.com>]

> > The doc string for a minor mode should tell
> > you it's a minor mode.
> 
> Should all minor modes say this?  Because there are more examples of
> modes that don't, such as:
> - display-line-numbers-mode
> - whitespace-newline-mode
> 
> This is just from taking a quick look.

Yes, IMO they should.  Otherwise, how will
users know?  (OK, there are ways...)

Knowing a command is a minor mode is very
important to understanding its use.  It's
could even be argued that it's the most
important thing to know about it.
____

More generally, I think a failing of some
minor-mode doc strings is that they don't
tell you the basics of what the doc string
of `define-minor-mode' tells you, e.g. how
to turn the mode on/off, both interactively
and from Lisp.

This related problem has been taken care of
here and there over the years, bit by bit,
from bug reports etc.  But I think the
problem is still present here and there.

Anyway, this bug report is only about
`whitespace-mode'.  If someone wants to
fix its problem along with that of other
minor-mode commands, please do.